linux-kernel - [PATCH] ACPI: CPPC: Fix enabling CPPC on AMD systems with shared memory

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Message-ID: <20220713175346.630-1-mario.limonciello@amd.com>
Date:   Wed, 13 Jul 2022 12:53:46 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     <mario.limonciello@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Len Brown" <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Sudeep Holla <sudeep.holla@....com>,
        Pierre Gondois <pierre.gondois@....com>
CC:     <perry.yuan@....com>, <ray.huang@....com>,
        <stable@...r.kernel.org>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] ACPI: CPPC: Fix enabling CPPC on AMD systems with shared memory

When commit 72f2ecb7ece7 ("ACPI: bus: Set CPPC _OSC bits for all
and when CPPC_LIB is supported") was introduced, we found collateral
damage that a number of AMD systems that supported CPPC but
didn't advertise support in _OSC stopped having a functional
amd-pstate driver. The _OSC was only enforced on Intel systems at that
time.

This was fixed for the MSR based designs by commit 8b356e536e69f
("ACPI: CPPC: Don't require _OSC if X86_FEATURE_CPPC is supported")
but some shared memory based designs also support CPPC but haven't
advertised support in the _OSC.  Add support for those designs as well by
hardcoding the list of systems.

Fixes: 72f2ecb7ece7 ("ACPI: bus: Set CPPC _OSC bits for all and when CPPC_LIB is supported")
Fixes: 8b356e536e69f ("ACPI: CPPC: Don't require _OSC if X86_FEATURE_CPPC is supported")
Link: https://lore.kernel.org/all/3559249.JlDtxWtqDm@natalenko.name/
Cc: stable@...r.kernel.org # 5.18
Reported-and-tested-by: Oleksandr Natalenko <oleksandr@...alenko.name>
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 arch/x86/kernel/acpi/cppc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/acpi/cppc.c b/arch/x86/kernel/acpi/cppc.c
index 734b96454896..8d8752b44f11 100644
--- a/arch/x86/kernel/acpi/cppc.c
+++ b/arch/x86/kernel/acpi/cppc.c
@@ -16,6 +16,12 @@ bool cpc_supported_by_cpu(void)
 	switch (boot_cpu_data.x86_vendor) {
 	case X86_VENDOR_AMD:
 	case X86_VENDOR_HYGON:
+		if (boot_cpu_data.x86 == 0x19 && ((boot_cpu_data.x86_model <= 0x0f) ||
+		    (boot_cpu_data.x86_model >= 0x20 && boot_cpu_data.x86_model <= 0x2f)))
+			return true;
+		else if (boot_cpu_data.x86 == 0x17 &&
+			 boot_cpu_data.x86_model >= 0x70 && boot_cpu_data.x86_model <= 0x7f)
+			return true;
 		return boot_cpu_has(X86_FEATURE_CPPC);
 	}
 	return false;
-- 
2.34.1